var s = "lang=zh-CN&token=-_71Y8qHna0Yz9D3I-BeTaI-exVWiFvXKazvMSH9-JokzDmuwzAMQMG7vJowKFKULN7mL87SKECCVIbvHgSuppudqSS-6KIIs5BFmEZ6qA5hOll6DKvRSrVWXZiVVGEGCcLPyS9pq7trL623tg4V_kkTNnLn9Xg__zYyVHUcwuX7qkevVodwJSluEUPVWke4ne2d1OMTAAD__w%3D%3D&access_key_id=9&appversion=6.7.46&channel=1100000002&_ds=&xpsid=ca21ad9b4e1c40ab9503187bf3918fae&xpsid_root=bffccde23e7845d19703cbec2579b724&area=32&flng=118.178&flat=24.49165&app_version=6.7.46";

var reg = new RegExp('(^|&)token=([^&]*)(&|$)', 'i');
var body = s
var r = body.substr(1).match(reg);
body = body.replace(unescape(r[2]), "123");  

console.log(body);